A method for decoding an image by a decoding apparatus comprises the steps of: obtaining merge with motion vector difference (MMVD) flag information of a current block from a bit stream; determining whether or not the current block is a current picture referencing (CPR) coding block; if the current block is a CPR coding block, deriving base motion information; deriving motion information of the current block on the basis of the base motion information; generating prediction samples of the current block on the basis of the motion information; and generating reconstruction samples of the current block on the basis of the prediction samples, wherein the MMVD flag information indicates whether or not motion information is derived when the MMVD is applied to the current block, and the CPR coding block is a block coded by using a current picture including the current block as a reference picture.
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2. The image decoding method of claim 1, wherein the base motion information is a firstly-ordered candidate among motion information candidates in a merge candidate list for the current block.
4. The image decoding method of claim 3, wherein when MMVD is applied to the current block and the current block is not a CPR coding block, there are two motion information candidates for the current block, and the MMVD candidate flag information is related to indicating one of the two motion information candidates.
5. The image decoding method of claim 4, wherein the two motion information candidates are a firstly-ordered candidate and a secondly-ordered candidate in a merge candidate list for the current block.
6. The image decoding method of claim 1, wherein the determining whether or not the current block is a CPR coding block determines that the current block is a CPR coding block when only one reference picture is included in a reference picture list for the current block and the one reference picture is the current picture.
9. The image encoding method of claim 8, wherein the base motion information is a firstly-ordered candidate among motion information candidates in a merge candidate list for the current block.
11. The image encoding method of claim 10, wherein when MMVD is applied to the current block and the current block is not a CPR coding block, there are two motion information candidates for the current block, and the MMVD candidate flag information is related to indicating one of the two motion information candidates.
12. The image encoding method of claim 11, wherein the two motion information candidates are a firstly-ordered candidate and a secondly-ordered candidate in a merge candidate list for the current block.
13. The image encoding method of claim 8, wherein the determining whether or not the current block is a CPR coding block determines that the current block is a CPR coding block when only one reference picture is included in a reference picture list for the current block and the one reference picture is the current picture.
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January 2, 2020
May 23, 2023
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